Bike-to-run bricks: when, how many, at what intensity

What a brick is for

Running off the bike is a different skill from running. Your cadence is wrong for the first minutes, your posture is set for a saddle, the muscles that have just been turning circles are asked to absorb impact instead, and your sense of pace lies to you: the effort feels enormous and the watch says you are slow. None of that is fitness, and none of it improves by being ignored until race day. The brick exists so that the strangeness happens in training, where it costs nothing, rather than in the first kilometre of a race you have prepared for months. That is familiarisation, and it is worth being honest about the limit: there is no good evidence that bricks make you run faster on race day. They make the transition known, not your legs quicker.

When they belong in the block

Early and regularly, short and easy at first, then weekly near the race. Because the point is familiarity rather than fitness, a brick costs little when its run leg is short and easy, so there is no reason to wait for the second half of the block to start. Leo's shape is one brick every other week from the second week of the block, then one every week across the last eight weeks, and none at all in race week — the day before a race is a short spin, and a brick that week is a session you cannot absorb in time. He places them on the long-ride day, because a brick simply is the long ride with the race's own run bolted onto the end.

How hard, and this is where people get it wrong

The ride carries the intensity your race format actually asks for — a short race is ridden near threshold, a long one is ridden at an endurance effort and stays there. The run that follows does not. It goes at the easy end of your pace band, deliberately, every time. The temptation is the opposite: you feel terrible off the bike, so you push to prove you can, and you turn a rehearsal into the hardest session of the week sitting on top of the longest ride of the week. That combination is a real risk: running causes most triathlon injuries (roughly 45 to 92% of them, depending on the study), and sudden jumps in running load are what tend to come before them. What you need to learn is what your normal easy pace feels like with tired legs, not how fast you can run while already wrecked.

How long the run should be

Proportionate to the race, not to your ambition. On a short-course race the run off the bike is brief — a few minutes are enough to teach the legs the transition — while on a long-distance build it stretches considerably, because there the brick rehearses fuelling as much as running. A useful rule: the brick run should never be so long that it compromises the next two days. If your Monday is ruined every time, the brick was a second long run in disguise.

Rehearse the transition, not just the running

The minutes between the two disciplines are part of the session. Rack the bike, change shoes, drink what you plan to drink, and go — without a fifteen-minute pause that turns the brick into two separate sessions. On race day the transition is a place people lose more time than they would ever gain from a better bike, and it is free to practise. The last few minutes of the ride matter too: spinning at a higher cadence before you get off makes the first kilometre noticeably less brutal.

What Leo does with bricks

Leo writes the brick as one session — the ride, the transition, then the run leg — rather than as two items that happen to be adjacent. He places them on the long-ride day, every other week from the second week of the block and every week across the last eight weeks, and prescribes the run part at the easy end of its band without exception. When you come back and your watch has saved two separate activities, Leo matches both to that single planned session instead of telling you that you missed it. What he will not do is tell you what your race-day run pace will be: he does not estimate an overall triathlon time, and he does not project splits. See Coach Leo for triathletes, or your format — olympic, half distance, full distance.

Frequently asked questions